JP7374968B2 - Flexible printed circuit board and recording head - Google Patents

Description

The present invention relates to a flexible printed circuit board that is capable of transmitting signals to a recording element substrate and also transmits signals from the recording element substrate to the outside, and a recording head equipped with the flexible printed circuit board.

A print head in a printing apparatus includes a print element substrate that can eject ink from nozzles by driving a print element. Such a print head is connected to a power supply board, a control board, etc. via a flexible printed circuit board with a laminated structure in order to transmit power and drive signals to the print element board. Since ink is ejected from the recording element substrate, the ink may adhere to a flexible printed circuit board connected to the recording element substrate. If ink adheres to the side of a flexible printed circuit board where the laminated surface is exposed and is not connected to other circuit boards, the ink will enter from the interface of the laminated layers, and the intruded liquid will cause damage to the vicinity of the side. There is a possibility that the arranged wirings may be short-circuited. This may cause damage to the recording head using the flexible printed circuit board.

In order to prevent ink from entering from the sides, it is conceivable to reinforce the sides with reinforcing plates, or to seal the sides with a sealing material, for example. Alternatively, as disclosed in Patent Document 1, it is possible to cover the target portion with a film.

Japanese Patent Application Publication No. 2010-27762

However, in the case of a configuration in which the side portion is reinforced with a reinforcing plate or the entire side portion is sealed, there is a risk that the flexible performance of the flexible printed circuit board may be degraded. Further, when using the technique of Patent Document 1, it becomes difficult to use the technique of Patent Document 1 if components such as a capacitor are mounted on a flexible board.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technology that can suppress damage to a recording head caused by a short circuit between wirings due to ink intrusion into the interior without deteriorating performance. shall be.

In order to achieve the above object, one embodiment of the present invention is connected at an end side to a printing element substrate capable of ejecting ink using a printing element, and transmits signals from a control unit in a printing apparatus via wiring. The flexible printed circuit board is capable of transmitting a signal to the recording element board via wiring, and is capable of transmitting a signal from the recording element board to the control unit via wiring, the flexible printed circuit board being on the side side of the high potential wiring. a regulating section that regulates ink from entering into the flexible printed circuit board ; a low-potential ground wiring and a low-potential signal line that monitors a signal value transmitted by the control section or an operation based on the signal; and a wiring section formed of the same, and the regulating section, the low-potential ground wiring, and the signal line are arranged in order from the side part side.

According to the present invention, it is possible to suppress damage to the recording head caused by short circuits between wiring lines due to ink intrusion.

FIG. 1 is a schematic configuration diagram of a recording head according to an embodiment. An enlarged view of frame II in FIG. 1. FIG. 2 is a cross-sectional view showing an example of wiring formed on a flexible substrate. FIG. 3 is a diagram illustrating ink intrusion from the side. FIG. 3 is a diagram illustrating ink intrusion from the side. FIG. 3 is a diagram showing a guard pattern formed on a flexible substrate. FIG. 3 is a diagram showing a wiring section formed on a flexible substrate. FIG. 3 is a diagram illustrating ink intrusion from a side portion where a guard pattern and a wiring portion are provided. FIG. 3 is a diagram illustrating details of a wiring section. FIG. 3 is a diagram illustrating details of a wiring section. Flowchart showing the procedure of reading processing. FIG. 3 is a diagram illustrating details of a wiring section. The figure which shows the modification of the specific example of a wiring part. The figure which shows the modification of the flexible board by embodiment.

Hereinafter, an example of an embodiment of a flexible printed circuit board and a recording head will be described with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention, and not all combinations of features described in the embodiments are essential to the solution of the present invention. Further, the relative positions, shapes, etc. of the structures described in the embodiments are merely examples, and the scope of the present invention is not limited to these.

<Configuration of recording head>
FIG. 1 is a schematic configuration diagram of a recording head equipped with a flexible printed circuit board according to a first embodiment. FIG. 1A is a schematic diagram of a print head used in a line type printing apparatus. FIG. 1B is a schematic configuration diagram of a print head used in a serial scan type printing apparatus. FIG. 1(c) is a schematic configuration diagram of a recording head including a pad directly connected to a circuit provided in the main body. FIG. 2 is an enlarged view of the frame II portion in FIG. 1(a). In the following description, the "flexible printed circuit board" will be appropriately referred to as a "flexible circuit board."

The recording head 100 shown in FIG. 1A is a recording head used in a line type recording apparatus. In the recording head 100, the flexible substrate 10 according to the present embodiment connects an electric wiring board 14 connected to a control unit (not shown) of the recording apparatus and a recording element substrate 16 capable of ejecting ink by driving a recording element. are doing. In the recording head 100, a plurality of recording element substrates 16 are arranged in parallel, and the area where the recording element substrates 16 are arranged in parallel has a length corresponding to the length in the width direction of the recording area that can be recorded by the recording apparatus. . The recording head 100 records an image on the recording medium by ejecting ink onto the recording medium that is conveyed in a direction intersecting the width direction.

As shown in FIG. 2, at one end of the flexible substrate 10, the wiring formed on the flexible substrate 10 is joined to the corresponding wiring on the electric wiring board 14 with a wire. Further, at the other end, the wiring formed on the flexible substrate 10 is connected to the corresponding wiring on the recording element substrate 16 with a wire. Thereby, the control section provided in the recording apparatus can output various signals and the like to the recording element substrate 16 via the electric wiring board 14 and the flexible substrate 10. The wires are generally made of aluminum, gold, or the like, and are joined by wedge bonding or the like. Although not shown in FIG. 2, the wires and their joints are sealed with a sealing material.

The print head 500 shown in FIG. 1B is a print head used in a serial scan type printing apparatus. In the print head 500, the flexible substrate 10 according to this embodiment connects an electric wiring board 14 connected to a control section of the printing apparatus and a print element board 16 that ejects ink by driving a print element. The recording head 500 alternately performs an ejection operation in which ink is ejected while moving in a direction intersecting the conveyance direction, and a conveyance operation in which the recording medium is conveyed in the conveyance direction, with respect to the recording medium conveyed in the conveyance direction. to record the image on the recording medium.

The chip unit portion consisting of the flexible substrate 10, the electrical wiring board 14, and the recording element substrate 16 basically has the same structure as the recording head 100. Note that the joining portion is not limited to wire, and may be joined by thermocompression bonding or the like. Furthermore, the electrical wiring board 14 and the flexible board 10 may be connected using a connector, and various known connection methods may be used.

The print head 600 in FIG. 1C is a print head used in a serial scan type printing apparatus, and has a configuration in which a unit consisting of a flexible substrate 10 and a print element board 16 can be connected to a tank in which ink to be ejected is stored. It becomes. In the recording head 600, the electrical wiring board 14 is not connected to one end of the flexible substrate 10 according to the present embodiment, and a pad 18 is provided to which signals from the control unit of the recording apparatus are input. . The other end is connected to the recording element substrate 16.

<Configuration of flexible printed circuit board>
As described above, regarding the flexible substrate 10 according to the present embodiment, there are no particular limitations on the connection method with the recording element substrate 16 or the like and the type of recording head that constitutes the flexible substrate 10. In other words, the flexible substrate 10 is capable of transmitting electrical signals output from the control unit of the recording apparatus to the recording element substrate 16, and also transmits signals from the recording element substrate 16 and transmitting them via the electrical wiring board 14 and the like. It can be output to a control unit, etc. In this embodiment, the recording element substrate 16 is configured to generate air bubbles in the ink by heating with a heater (recording element) and eject ink droplets.

The flexible substrate 10 often has a structure in which a plurality of layers are stacked in order to be able to apply a large amount of current, increase the number of signal lines, and support communication using LVDS (Low Voltage Differential Signaling). FIG. 3 is a cross-sectional view of a flexible substrate with a laminated structure, in which (a) is an example of a flexible substrate with a two-layer structure, and (b) is an example of a flexible substrate with a four-layer structure.

The flexible substrate 10 having a two-layer structure includes a base material 302, and copper wiring is laid on a front surface 302a and a back surface 302b of the base material 302. An adhesive 316 is applied to the front surface 302a and the back surface 302b on which the wiring is laid, and the coverlay 304 is attached to the adhesive 316. 3A and 3B are cross-sectional views of the flexible substrate 10 taken in a direction intersecting the direction in which the wiring extends. Therefore, both side portions 10c and 10d, which correspond to the side surfaces of the flexible substrate 10 in FIGS. 3(a) and 3(b), are exposed to space when attached to the recording head as shown in FIG. It has become.

The wiring arrangement in the cross section of the flexible substrate 10 is, for example, as shown in FIG. 3(a). In FIG. 3A, a data line 306 such as an LVDS signal line is formed between VSS lines 308 on the front surface 302a. Further, on the back surface 302b, in a region corresponding to the region where the data wire 306 and the VSS wire 308 on the front surface 302a are formed, a VSS wire 308, which is a low voltage ground, is provided to maintain signal quality from external noise. It is provided. In other words, this flexible substrate 10 is subjected to impedance matching.

On the front surface 302a, various other signal lines 310 are also formed in the vicinity of the side parts 10c and 10d of the flexible substrate 10, and on the back surface 302b, VSS wiring is formed in an area corresponding to the area where the signal line 310 is formed. 308 is formed. Further, on the front surface 302a and back surface 302b of the base material 302, a VH wiring 312 and a GNDH wiring 314, which are high-potential heater power sources, are provided running in parallel at mutually corresponding positions. The reason why the VH wiring 312 and the GNDH wiring 314 are provided in parallel is to achieve a capacitor effect and to suppress current changes due to the influence of the L component. Since the VH wiring 312 and the GNDH wiring 314 carry a large current, they are formed thicker than other wirings to prevent heat generation. Note that the VH wiring 312 and the GNDH wiring 314 are formed by forming the VH wiring 312 as a thick wiring on the front surface 302a, and forming the GNDH wiring 314 as a thick wiring on the back surface 302b in an area corresponding to the area where the VH wiring 312 is formed. may be formed.

Although not shown in FIG. 3A, in the two-layer flexible substrate 10, the same signal lines on the front surface 302a and the back surface 302b are connected to each other through through holes. Further, in many cases, a pad (shown as an electrical connection pad in FIG. 2) for an electrical connection with the electrical wiring board 14 is formed on one of the front and back surfaces of the flexible board 10. Therefore, in this case, in the flexible substrate 10, the wiring is concentrated on the surface where the pad is provided.

The flexible substrate 10 having a four-layer structure includes a base material 322, and wiring is laid on a front surface 322a and a back surface 322b of the base material 322. An adhesive 336 is applied to the surface 322a on which the wiring is laid, and a base material 344 is attached to this adhesive 336. On the surface 344a of the base material 344, wiring is laid and an adhesive 336 is applied, and the coverlay 324 is attached via the adhesive 336. Further, an adhesive 336 is applied to the back surface 322b on which the wiring is laid, and a base material 346 is attached to this adhesive 336. On the back surface 346b of the base material 346, wiring is laid and an adhesive 336 is applied, and the coverlay 324 is attached via the adhesive 336.

Compared to a two-layer structure, the four-layer flexible substrate 10 has more layers, so it has a higher degree of freedom in designing wiring, etc., and VH wiring, GNDH wiring, signal lines, etc. can be formed on different layers. can do. Hereinafter, in the flexible substrate 10 shown in FIG. 3(b), the layer formed on the surface 344a of the base material 344 will be described as a first layer, and the layer formed on the surface 322a of the base material 322 will be described as a second layer. . Further, the layer formed on the back surface 322b side of the base material 322 will be described as a third layer, and the layer formed on the back surface 346b side of the base material 346 will be described as a fourth layer.

The first layer is mainly a layer in which data wiring 326 such as an LVDS signal line and various signal lines 330 are formed. The second layer is a layer in which the VSS wiring 328 is mainly formed in order to form the VSS wiring 328 in a region corresponding to the data wiring 326 and signal line 330 of the first layer. The third layer is a layer in which VH wiring 332, which is a high potential power source, is mainly formed. The fourth layer is a layer in which a GNDH wiring 334, which is a high voltage ground, is mainly formed. In the third and fourth layers, VSS wiring 328 is formed near the side portions 10c and 10d of the flexible substrate 10.

In FIG. 3(b), since a cross section is shown at a predetermined position in the extending direction of the wiring, no through holes are shown except for the VSS wiring 328, but the same wiring in different layers has through holes. connected with. Each wiring is concentrated on a surface with a pad (electrical connection pad). The types of wiring and their positions shown in FIGS. 3(a) and 3(b) are merely examples.

Here, the side portions 10c and 10d of the flexible substrate 10 are exposed to the space in the recording head. Therefore, ink ejected from the recording element substrate 16 may adhere to the side portions 10c and 10d of the flexible substrate 10. Furthermore, as described above, the flexible substrate has a structure in which a coverlay is attached via an adhesive to a base material on which wiring is formed. Therefore, in the case of highly permeable ink, if the ink adheres to the side parts 10c and 10d, the ink may enter from the adhesive surface, that is, the interface between the base material and the coverlay and the adhesive. Ta.

When ink enters from the adhesive surface, adjacent wirings formed in the layer into which the ink has entered are connected by the ink, resulting in a short circuit. For example, if this short-circuited wiring includes high-potential wiring such as a heater power source, the recording head may be damaged, such as smoke or ignition, or failure of the recording element board 16 or the control section of the recording device. It is possible that

For example, when ink enters from the side of a four-layer flexible substrate, a situation as shown in FIG. 4 occurs. FIG. 4 is a diagram showing a state in which ink has entered from one side of a flexible substrate having a four-layer structure. On one side 10c side of the flexible substrate 10, a low potential VSS wiring 402 and a high potential VH wiring 404 are formed adjacent to each other in the third layer. When ink enters from the side portion 10c, the VSS wiring 402 and the VH wiring 404 in the third layer are electrically connected by the ink, resulting in a short circuit. When this short circuit occurs, a large current flows where normal current does not flow, causing destruction or burnout due to heat generation in the flexible substrate 10, electrical wiring board 14, and recording element substrate 16, and damaging the recording head. Sometimes it happens.

The same applies to a two-layer flexible substrate. FIG. 5 is a diagram showing a state in which ink has entered from the other side of a two-layered flexible substrate. 5(a), (b), and (c) show a state in which ink has entered the upper layer, and FIG. 5(d), (e), and (f) show a state in which ink has entered the lower layer. Note that the upper layer is a layer formed on the surface side of the base material, and is also referred to as the first layer. Further, the lower layer is a layer formed on the back side of the base material, and is also referred to as the second layer.

In the flexible substrate 10 shown in FIGS. 5A, 5B, and 5C, a VSS wiring 502, which is a low-potential ground wiring, is formed on the other side 10d side of the upper layer. Further, a signal line 504 is formed next to the VSS wiring 502, in which a change in the signal value cannot be detected even if it is short-circuited with the VSS wiring 502. The signal line 504 is a wiring in which the signal value transmitted via the signal line 504 is not monitored, or is not monitored much during normal operation. Furthermore, a high potential GNDH wiring 506 is formed next to the signal line 504. Note that in FIGS. 5A, 5B, and 5C, the wiring closer to one side portion 10c than the VH wiring 512 is omitted.

When ink enters this upper layer, more specifically, when ink enters from the interface between the base material 508 and adhesive 510 in the upper layer, the ink first contacts the VSS wiring 502 (see FIG. 5(a) reference). Then, as the ink advances, the ink comes into contact with the signal line 504, and the VSS wiring 502 and the signal line 504 are electrically connected by the ink (see FIG. 5(b)). Note that the signal line 504 is a wiring that will not be damaged even if it is short-circuited with the VSS wiring 502, and since the signal value is not often monitored via the flexible substrate 10, the signal line 504 that has changed due to the short-circuit will not be damaged. The transmitted signal value cannot be detected.

After that, as the ink further advances, the ink comes into contact with the GNDH wiring 506, and the GNDH wiring 506, the signal line 504, and the VSS wiring 502 are electrically connected by the ink (see FIG. 5(c)). . As a result, the signal line 504 and the VSS wiring 502 are short-circuited through the ink, causing a large current to flow, causing smoke and fire damage in the flexible substrate 10, the recording element substrate 16, or the control section.

In the flexible substrate 10 shown in FIGS. 5(d), (e), and (f), VSS wiring 502, GNDH wiring 506, and VH wiring 512 are arranged on the front and back surfaces of the base material 508, respectively, from the other side 10d side. is formed. Note that in FIGS. 5(d), (e), and (f), the wiring closer to one side portion 10c than the VH wiring 512 is omitted.

When ink enters the lower layer of the flexible substrate 10 from the other side 10d of the flexible substrate 10, the ink first contacts the VSS wiring 502 (see FIG. 5(d)). Then, as the ink advances, the ink comes into contact with the GNDH wiring 506, and the VSS wiring 502 and the GNDH wiring 506 are electrically connected by the ink (see FIG. 5(e)). Note that since both the VSS wiring 502 and the GNDH wiring 506 are at ground potential, it is difficult to detect an abnormality even if a short circuit occurs between these wirings.

After that, as the ink further advances, the ink comes into contact with the VH wiring 512, and the VH wiring 512, GNDH wiring 506, and VSS wiring 502 are electrically connected by the ink (see FIG. 5(f)). . As a result, the VH wiring 512 and the GNDH wiring 506 are short-circuited through the ink, and a large current flows, causing smoke or fire damage in the flexible substrate 10, the recording element substrate 16, or the control section.

<Characteristic configuration of the flexible printed circuit board according to this embodiment>
In this manner, in the flexible substrate 10, even if ink enters from the side portions 10c and 10d, it is not possible to detect an abnormality in the print head unless burnout or the like occurs and the print head does not function normally. Although it is conceivable to add a new configuration that can detect a short circuit between the wiring arranged on the sides 10c and 10d, new problems such as increasing the size of the flexible substrate 10 arise. Therefore, in this embodiment, a configuration is adopted in which the intrusion of ink into the flexible substrate 10 can be detected as an abnormality in the recording head without providing a new configuration.

FIG. 6 is a cross-sectional view of the side and vicinity of the flexible substrate according to this embodiment. In the following description using FIG. 6, the configuration on the other side 10d of the flexible substrate 10 will be explained as an example, but the configuration shown in FIG. 6 may be applied to one side 10c. Further, in FIG. 6, the upper layer wiring and the lower layer wiring are arranged in the same way from the sides, but the invention is not limited to this. That is, the configuration shown in FIG. 6 may be provided in either the upper layer or the lower layer. Furthermore, although FIG. 6 shows a flexible board with a two-layer structure as an example, the configuration of FIG. 6 may be applied to a flexible board with a single-layer structure, or a flexible board with more than two layers. It may be applied to at least one layer of the substrate.

In the flexible substrate 10 according to this embodiment, the guard pattern 602 is provided closest to the side portion 10d. Further, a wiring portion 603 is provided next to the guard pattern 602, which can detect ink intrusion due to short circuit. The wiring for the wiring section 603 is not a new wiring, but a wiring provided on a general flexible substrate is formed next to the guard pattern 602 as the wiring section 603. Specifically, the wiring section 603 connects, for example, a low-potential anode signal line 604 whose transmitted signal value is monitored relatively frequently and a low-voltage ground wiring, in this embodiment a VSS wiring 606. It has two wires. The guard pattern 602 and the wiring section 603 will be described in detail below.

=Guard pattern=
The guard pattern 602 is formed, for example, at the side portion 10d so as to be longer in the height direction than other wirings and to come into contact with the base material 608 and the coverlay 610 (see FIG. 6(a)). Further, for example, the guard pattern 602 has the same length in the height direction as other wiring on the base material 608 in the vicinity of the side portion 10d, and an adhesive 612 exists between it and the coverlay 610. (See FIG. 6(b)). Note that the height direction is the lamination direction in the flexible substrate 10, that is, the thickness direction. In this way, since the guard pattern 602 is formed within the layer in which wiring is formed, the flexible performance of the flexible substrate 10 is unlikely to deteriorate.

The guard pattern 602 is configured so as not to be electrically connected to the electrical wiring board 14 and the recording element board 16. The material constituting the guard pattern 602 may be a metal material or a non-metal material. Examples of the nonmetallic material include nonconductive materials such as resin, film, and rubber.

When the guard pattern 602 is provided on the side portion 10d as shown in FIG. 6(a), it is preferable to use a non-metallic material. In this case, as the material for forming the guard pattern 602, it is preferable to use a material that has high adhesion to the base material 608 and the coverlay 610 and that is difficult for ink to penetrate. Further, it is more preferable that the material is highly adhesive not only to the base material 608 and the coverlay 610 but also to the adhesive 612. A material that is difficult for ink to penetrate is, for example, a material that has low affinity for ink ejected from a recording head. When the guard pattern 602 is formed on the side portion 10d as shown in FIG. It will be done.

When the guard pattern 602 is made of a metal material, if the guard pattern 602 is configured to be energized, moisture remaining on the surface may be electrolyzed or anodic oxidized, leading to corrosion, and the adhesive may It becomes easy to peel off from 612 and the like. Therefore, when using a metal material, the guard pattern 602 is in a state where it is not electrically connected (electrically floating), that is, it is not energized. Or connect it to an independent ground. When a metal material is used, corrosion of the metal material can be suppressed by, for example, a configuration as shown in FIG. 6(b). In the case of the configuration shown in FIG. 6(a), a metal material with high corrosion resistance is used. In the case of the configuration shown in FIG. 6B, the guard pattern 602 can be formed, for example, in the process of forming other wirings. Therefore, in this case, the guard pattern 602 is made of copper.

=Wiring section=
Next, the wiring section 603 provided next to the guard pattern 602 will be explained. FIG. 7 is a diagram showing a wiring section provided next to the guard pattern. FIG. 7A is an enlarged view of the frame Va in FIG. 2. FIG. FIG. 7B is a transparent view of the wiring on the back side in the frame VIIa of FIG. 2, seen from the front side. FIG. 7(c) is a sectional view taken along the line VIIc-VIIc in FIG. 7(a). FIG. 7(d) is an enlarged view of the frame VIId in FIG.

In the upper and lower layers of the flexible substrate 10 in FIG. 7, a guard pattern 602 is formed closest to the side portion 10d. A VSS wiring 606 which is a low potential ground wiring is formed next to the guard pattern 602, and an anode signal line 604 is formed next to the VSS wiring 606. In the upper layer, a GNDH wiring 702 is formed next to the anode signal line 604, and a VH wiring 704 is formed next to the GNDH wiring 702 (see FIG. 7(a)). On the other hand, in the lower layer, a VSS wiring 606 is formed next to the anode signal line 604, a GNDH wiring 702 is formed next to the VSS wiring 606, and a VH wiring 704 is formed next to the GNDH wiring 702 (see FIG. 7(b)). ).

When the anode signal line 604 is connected to the VSS wiring 606 and short-circuited, the control unit can detect an abnormality occurring in the anode signal line 604. That is, the signal value on the anode signal line 604 is monitored by the control unit, and the control unit is configured to be able to detect abnormalities in the signal from the anode signal line 604 based on the result of the monitoring. For example, the anode signal line 604 is preferably a signal line of a temperature detection diode (temperature sensor) whose signal value is constantly monitored in the control unit. Note that the anode signal line 604 is not limited to a signal line for a temperature detection diode, but is a signal line that monitors signal values in the control unit, and is electrically connected to low potential wiring such as the VSS wiring 606. Any signal line may be used as long as it causes an abnormal signal value when it is connected to a short circuit. The low potential is, for example, 6V or less, and the high potential is, for example, 10V or more.

Furthermore, the anode signal line 604 may be a wiring that falls to the ground, that is, short-circuits with a low-potential wiring such as the VSS wiring 606, thereby making it impossible for the control unit to perform normal control. Alternatively, it may be a signal line through which the control unit notifies an error based on a signal value. The anode signal line 604 excludes wiring related to driving a heater, which is a printing element for ejecting ink, a sub-heater for adjusting the temperature of the printing element substrate 16, and the like.

When the anode signal line 604 is a signal line for a temperature detection diode, if ink enters from the side 10d of the flexible substrate 10 and the anode signal line 604 and the VSS wiring 606 are electrically connected and short-circuited by the ink, the control Temperature control by section becomes impossible. As a result, the control unit determines that there is an abnormal state, and, for example, the drive of the print head is stopped.

= Formation range of guard pattern and wiring part =
On the end side of the flexible substrate 10 (that is, the end side connected to the electric wiring board 14 and the recording element substrate 16), the GNDH wiring 702 connected by through holes in each layer is located at the position shown in FIG. 7(d). It is formed. The reason why the GNDH wiring 702 is formed at the position shown in FIG. 7(d) is that the pad of the GNDH wiring on the substrate to be connected on the end side is formed at a position corresponding to the position.

In the flexible substrate 10 constituting the recording head, ink is most likely to adhere to the area near the end of the flexible substrate 10 where it is connected to the recording element substrate 16 by a wire. Although not shown in FIG. 7(d), the part where the wires are connected is covered with a sealant to prevent short circuits between the wires due to ink adhesion (see Figure 7(d)). 7(d) (see dashed box). In the area sealed with this sealing material, the sealing material prevents ink from penetrating, so a guard pattern is formed on the end side where the recording element substrate 16 is connected from the area sealed with the sealing material. 602 and the wiring portion 603 may not be formed. That is, in the configuration in which the guard pattern 602, the anode signal line 604, and the VSS wiring 606 are arranged in this order from the side part 10d side, the cut (end) of the sealing material is not covered with the sealing material. It suffices if it is formed in the area.

Regarding the configuration in which the guard pattern 602, the anode signal line 604, and the VSS wiring 606 are arranged in this order from the side part 10d side, in FIG. so that it is formed uniformly. However, such a configuration may be formed only in a part of the region on the side portion 10d side. Specifically, for example, it may be formed only in a region corresponding to a portion to which ink adheres, that is, a portion to which ink may adhere or a portion to which ink tends to adhere. Alternatively, it may be formed only in a region corresponding to a portion where a high-potential power supply system is arranged.

=Function of guard pattern and wiring part=
In the above configuration, a case where ink enters from the side portion 10d of the flexible substrate 10 will be described. FIGS. 8(a), 8(b), and 8(c) are diagrams showing, in chronological order, a state in which ink enters from the side of a flexible substrate provided with a guard pattern and a wiring portion. Note that in FIG. 8 (FIGS. 6 and 7), a guard pattern 602, a VSS wiring 606, and an anode signal line 604 are formed in order from the side portion 10d in the upper layer and the lower layer. In this upper layer and lower layer, the same wirings are connected to each other by through holes.

When ink enters from the interface between the upper base material 608 and the adhesive 612 in the side portion 10d of the flexible substrate 10, the ink first reaches the guard pattern 602 (see FIG. 8(a)). As the ink continues to penetrate, the ink reaches the VSS wiring 606 (see FIG. 8B), and the guard pattern 602 and the VSS wiring 606 are electrically connected via the ink. Note that since the guard pattern 602 is in an electrically floating state, that is, it is not energized, no major abnormality that would damage the recording head occurs at this stage. Therefore, the control section of the recording apparatus connected via the electrical wiring board 14 will not detect any abnormality.

As the ink penetrates further, the ink reaches the anode signal line 604 (see FIG. 8(c)), and the VSS wiring 606 and the anode signal line 604 are electrically connected through the ink, resulting in a short circuit. . The anode signal line is, for example, a signal line for a temperature detection diode, and the control section always detects the temperature of the recording element substrate 16 based on the signal value from the signal line. Therefore, a short circuit between the VSS wiring 606 and the anode signal line 604 causes an abnormality in the signal value input from the anode signal line 604, and based on this abnormality, the control unit detects that an abnormality has occurred in the recording head. Detect. In this case, the abnormality of the recording head detected by the control section is more specifically a failure of the temperature detection diode or a short circuit in the flexible substrate 10. Then, based on the determination that an abnormality has occurred, the control section stops driving the recording head, notifies that an abnormality has occurred, and so on.

In this way, the wiring section 603 is configured to be able to detect ink intrusion, and the guard pattern 602 safely delays the time until the wiring section 603 detects ink intrusion. Furthermore, the guard pattern 602 functions as a regulating portion that regulates ink intrusion.

=Specific configuration of wiring section=
In this way, in the flexible substrate 10 according to the present embodiment, the guard pattern 602 is provided on the side part side, and the wiring part 603 that can detect ink intrusion is formed next to the guard pattern 602. The wiring section 603 capable of detecting ink intrusion is composed of two wirings. These two wiring lines are not newly provided only to detect ink intrusion, but are a combination of two wiring lines provided on a general flexible substrate that constitutes a print head.

The wiring portion 603 adjacent to the guard pattern 602 and capable of detecting ink intrusion will be described in more detail using a specific example. For ease of understanding, the explanation of the wiring section 603 for detecting ink intrusion adjacent to the guard pattern 602 using FIG. 9 etc. uses a wiring pattern without the guard pattern 602. I will explain. FIG. 9A is a diagram showing an example of a wiring pattern formed on a flexible substrate according to the prior art. FIG. 9(b) is a diagram showing a state in which ink has entered from the side of the flexible substrate in FIG. 9(a). The state in which the ink has entered as shown in FIG. 9B is just an example, and the ink does not necessarily enter from near the central portion of the side portion as shown. Note that, for ease of understanding, FIGS. 9A and 9B show wiring patterns formed on predetermined layers of the flexible substrate.

In the flexible substrate 900 in FIG. 9A, for example, a reset signal line (RESRT) 902 is formed on the side closest to one side 900c, and a latch signal line (LATCH) 904 is formed next to the reset signal line 902. There is. Here, the reset signal transmitted via the reset signal line 902 is a digital signal with a valid value that is transmitted only once when the power is turned on. Furthermore, the latch signal transmitted via the latch signal line 904 is a digital signal with a valid value that is transmitted each time during recording to confirm data. These signals are transmitted from a control unit (not shown) of the recording device via the electrical wiring board 14, and have the same driving ability.

Assume that ink enters from the side portion 900c of the flexible substrate 900 (see region 906 in FIG. 9(b)), and the reset signal line 902 and latch signal line 904 are electrically connected and short-circuited. The reset signal remains a ``0'' after transmitting a ``1'' for several microseconds at power-on. However, since the driving capabilities of the reset signal and the latch signal control section are the same, the latch signal is not necessarily changed to "0" due to the short circuit. Therefore, the latch signal output from the control section is transmitted as it is to the recording element substrate 16, and the recording element operates normally, but the control section may not be able to detect an abnormality, that is, an intrusion of ink. Note that the digital signal "1" indicates the power supply voltage of the digital circuit, and the digital signal "0" indicates the ground voltage.

Furthermore, in the flexible substrate 900, for example, an error signal line (ERROR) 910 is formed on the othermost side 900d, and a temperature sensor signal line (DIK) 912 is formed next to the error signal line 910. Therefore, when ink enters from the side portion 900d, the error signal line 910 and the temperature sensor signal line 912 are electrically connected and short-circuited (see region 908 in FIG. 9(b)). The error signal is a digital output signal that returns information from the recording element board 16 to the control unit as to whether or not data reception was performed normally. The recording element board 16 outputs "1" when the received data is not normal (for example, a part of the data is missing), and outputs "0" when the data can be received normally.

As the temperature sensor, for example, a diode is used to detect the temperature of the recording element substrate 16. The temperature sensor signal is an analog signal, and the temperature sensor signal output from the recording element substrate 16 is converted into a digital signal in the control section. Temperature sensor signal line 912 is connected to the cathode terminal of the diode, and its voltage is the ground voltage. In this way, both the error signal and the temperature sensor signal become the ground voltage during normal operation. Therefore, even if error signal line 910 and temperature sensor signal line 912 are short-circuited due to ink intrusion, the signal voltage does not change, and the control unit may not be able to detect an abnormality, that is, ink intrusion.

Therefore, as the wiring section 603 capable of detecting ink intrusion, two wirings satisfying the following conditions are formed adjacent to each other. The first condition is that the output value from one wiring or the operation based on the output value is monitored by the control unit. The second condition is that even if one wiring and the other wiring are short-circuited, the flexible substrate 10, electric wiring board 14, and recording element substrate 16 that constitute the control unit and the recording head will not be damaged.

(Specific example 1)
FIG. 10 is a diagram illustrating an example of a wiring section that allows the control section to detect ink intrusion. Specifically, as shown in FIG. 10, in the flexible substrate 1000, a VSS wiring 606 is formed closest to the side part 1000c as a wiring part 603 capable of detecting ink intrusion, and a latch signal line is formed next to the VSS wiring 606. 904 is formed. The latch signal driving ability of the control unit is low, on the order of several milliamps, the input impedance of the latch signal receiving circuit on the recording element substrate 16 is sufficiently high, and the impedance of the VSS wiring 606 is sufficiently low. Therefore, if ink enters from the side portion 1000c and the VSS wiring 606 and the latch signal line 904 are short-circuited, the latch signal is fixed to the ground voltage. Since the latch signal is a logical value, if it is fixed at the ground voltage, data will not be latched and the recording element (heater in this embodiment) will not be driven.

Here, the control section periodically reads the temperature of the recording element substrate 16 in order to maintain the recording quality constant. When the recording element substrate 16 has a relatively large area, there is a temperature distribution within the recording element substrate 16, so temperature sensors (not shown) are arranged at a plurality of locations within the recording element substrate 16. These temperature sensors are connected to a multiplexer (not shown) within the recording element substrate 16. When reading the value of each temperature sensor, data for selecting any one temperature sensor is sent from the control unit to the recording element board 16, and the temperature information of the selected temperature sensor is sent to the temperature signal via the multiplexer. An analog signal is sent from line 1002 to the control unit. Also, to ensure that the multiplexer switching based on the data that selects the temperature sensor is successful, at least one terminal of the multiplexer must be connected to a voltage that is far from the normal temperature signal, e.g., the supply voltage or ground. connected to voltage.

Referring to FIG. 11, the procedure of the reading process for reading the temperature using the temperature sensor will be described. In the explanation using FIG. 11, it is assumed that the recording element substrate 16 is provided with three temperature sensors and a four-channel multiplexer connected to the three temperature sensors and one VSS. FIG. 11 is a flowchart showing a detailed processing routine of the reading process.

When the reading process is started, first, the control unit outputs a signal to switch the channel in the multiplexer to the first channel (S1102). The multiplexer acquires the first temperature in the first temperature sensor corresponding to the first channel based on the switching signal to the first channel output from the control unit, and converts the acquired first temperature into an analog signal to generate a temperature signal. It is output to the control unit via line 1002 (S1104). This analog signal is converted into a digital signal by an analog-to-digital converter (A/D converter) in the control section.

Next, the control unit determines whether or not the first temperature is within the normal temperature range (S1106), and if it is determined that the first temperature is not within the normal temperature range, the control unit stops recording and sets the recording head to It is notified that an abnormality has occurred (S1108), and the reading process is ended. Further, if it is determined in S1106 that the first temperature is within the normal temperature range, the control unit outputs a signal to switch the multiplexer channel to the second channel (S1110). The multiplexer acquires the second temperature in the second temperature sensor corresponding to the second channel based on the switching signal to the second channel output from the control unit, and converts the acquired second temperature into an analog signal to generate a temperature signal. It is output to the control unit via line 1002 (S1112).

Thereafter, the control unit determines whether the second temperature is within the normal temperature range (S1114), and if it is determined that the second temperature is not within the normal temperature range, the process proceeds to S1108. Further, if it is determined in S1114 that the second temperature is within the normal temperature range, the control unit outputs a signal to switch the multiplexer channel to the third channel (S1116). The multiplexer acquires the third temperature in the third temperature sensor corresponding to the third channel based on the switching signal to the third channel output from the control unit, and converts the acquired third temperature into an analog signal to generate a temperature signal. It is output to the control unit via line 1002 (S1118).

Upon acquiring the third temperature, the control unit determines whether the third temperature is within the normal temperature range (S1120), and if it is determined that the third temperature is not within the normal temperature range, the process proceeds to S1108. Further, if it is determined in S1120 that the third temperature is within the normal temperature range, the control unit outputs a signal to switch the multiplexer channel to the fourth channel (S1122). The multiplexer is connected to VSS connected to the fourth channel based on the switching signal to the fourth channel output from the control unit, and obtains the ground voltage (S1124). Then, the control unit determines whether the acquired ground voltage is normal (S1126).

The control unit determines that the ground voltage is normal if it is, for example, 0.3V or less. If it is determined in S1126 that it is normal, the process returns to S1102. Further, if it is determined in S1126 that it is not normal, the process advances to S1108. Note that the channel switching period of the multiplexer is, for example, 8 milliseconds.

When ink enters from the side portion 1000c of the flexible substrate 1000 and the VSS wiring 606 and the latch signal line 904 are electrically connected and short-circuited, the latch signal, which is a valid value, is fixed to the ground voltage. The data sent to the recording element substrate 16 is determined by the latch signal. Therefore, if the data is not latched, even if the data is transmitted normally, it will not be confirmed by the recording element board 16, and the multiplexer channel will not be switched.

For example, if the multiplexer has been switched to the second channel the last time the latch signal was normally transmitted to the recording element substrate 16, the control section sends data to the recording element substrate 16 to switch the multiplexer to the third channel. Send to. However, if the VSS wiring 606 and the latch signal line 904 are short-circuited, the data will not be determined on the recording element board 16, and the switching to the third channel will not be performed, causing the control unit to 2 temperatures are output.

As a result, the control unit recognizes the input second temperature as temperature information of the third temperature sensor, but since the normal temperature ranges of the plurality of temperature sensors are usually the same, the temperature inside the recording element substrate 16 is It falls within a predetermined range of temperature distribution, for example, within 10°C. Therefore, even if the second temperature is received as temperature information from the third temperature sensor, the control unit recognizes that the temperature is within the normal temperature range, and performs processing to switch the multiplexer to the fourth channel. Thereafter, the control unit determines whether the ground voltage is normal or not, but since the multiplexer is not switched in the recording element substrate 16, the voltage at the second temperature is input to the control unit. For example, if the temperature characteristic of a temperature sensor is 0.65V at 25°C, the rate of change is -2mV/°C, and the normal temperature range is 0 to 100°C, it will be 0.5V at 100°C, so the ground voltage This will exceed the normal range (less than 0.3). Therefore, the control unit assumes that an abnormality has occurred in the temperature detection mechanism and stops recording, and also notifies the occurrence of the abnormality.

In this way, by configuring the wiring section 603 that can detect ink intrusion using the VSS wiring 606 and the latch signal line 904 (corresponding to the anode signal line 604), the latch signal can be dropped to the ground voltage due to ink intrusion. I can do it. Since the driving ability of the latch signal is low, even if the latch signal line 904 and the VSS wiring are short-circuited, there is a low possibility that the control unit, the recording element substrate 16, etc. will be immediately damaged. Therefore, by configuring the wiring section 603 that can detect ink intrusion using the VSS wiring 606 and the latch signal line 904, it is possible to detect an abnormality in the print head without damaging the print element substrate 16 or the control section. , it becomes possible to detect ink intrusion.

(Specific example 2)
FIG. 12 is a diagram illustrating another example of a wiring section that allows the control section to detect ink intrusion. As another specific example, the wiring section 603 includes a temperature sensor signal line (DIA) 1202 for a temperature sensor that is not connected to a multiplexer and is provided independently among a plurality of temperature sensors arranged on the printing element substrate 16. and a VSS wiring 606 (see FIG. 12). In FIG. 12, a VSS wiring 606 is arranged on the other side 1000d, and a temperature sensor signal line 1202 is formed next to the VSS wiring 606.

The input impedance of the A/D converter provided in the control section is sufficiently high, and the driving capability of the temperature sensor driving circuit is low, at 1 milliampere or less. Therefore, when liquid enters from the side portion 1000d (see region 908 in FIG. 12), the temperature sensor signal line 1202 and the VSS wiring 606 are connected by the ink and short-circuited. This short circuit causes the temperature sensor signal to become the ground voltage.

Assuming that the temperature characteristic of the temperature sensor is 0.65V at 25°C, the rate of change is -2mV/°C, and the normal temperature range is 0 to 100°C, when the temperature sensor signal becomes the ground voltage, the control unit will detect that the temperature is 300°C. Recognize that there is. For example, if the control unit is designed to determine that an abnormal temperature rise has occurred when the temperature exceeds 100°C, in this case, the control unit will determine that an abnormality has occurred in the recording head due to the abnormal temperature rise. In addition to stopping recording, it is possible to notify that the abnormality has occurred.

Note that arranging the analog signal temperature sensor signal line 1202 and the VSS wiring 606 next to each other is also effective in suppressing the influence of external noise on the analog signal. Further, by arranging the VSS wiring 606 on the side portion 1000d side, the temperature sensor signal line 1202 can be reliably lowered to the ground voltage. Furthermore, since the temperature sensor drive circuit is a constant current circuit that outputs, for example, 0.2 milliamperes, there is a low possibility that the temperature sensor drive circuit will malfunction even if the temperature sensor signal line 1202 is shorted to the VSS wiring 606.

Of the side parts 1000c and 1000d, one may be provided with the configuration of Specific Example 1, and the other side may be provided with the configuration of Specific Example 2 (see FIG. 13(a)). FIGS. 13(a) and 13(b) are diagrams showing a modification of the specific example of the wiring section. This makes it possible to detect abnormalities caused by ink entering from both sides of the flexible substrate 10. Furthermore, if it is difficult to change the terminal arrangement of the recording element substrate, the VSS wiring may be formed on the sidemost side using another layer, as shown in FIG. 13(b). Although not shown, a guard pattern 602 is provided on the side of the wiring section 603.

As described above, the flexible substrate 10 according to the present embodiment includes the guard pattern 602 that is not energized on the side or the sidemost side. Furthermore, a wiring section 603 is provided next to the guard pattern 602 to allow detection of ink intrusion. The wiring section 603 is composed of a low-potential ground wiring and a signal value and an anode signal line whose operation based on the signal value is monitored. The guard pattern 602 and the wiring section 603 are formed at a position where a high potential wiring is arranged at least in the vicinity thereof.

As a result, even if ink enters from the side of the flexible substrate 10, the ground wiring and the anode signal line are short-circuited before the ink reaches the high-potential wiring and short-circuits the wiring and the tie wiring. do. Since the anode signal line is monitored for its signal value or operation based on the signal value, abnormalities in the signal value or operation due to short circuits can be confirmed. In other words, it is possible to detect that the print head no longer operates normally due to ink entering the flexible substrate 10 without damaging other members constituting the print head.

Furthermore, the presence of the guard pattern 602 can delay the timing of short circuit between the ground wiring and the anode signal line. Thereby, the time during which the recording head can be used normally can be increased.

<Other embodiments>
Note that the above embodiment may be modified as shown in (1) to (4) below.

(1) Although not particularly described in the above embodiments, a four-layer flexible substrate has a configuration as shown in FIGS. The configuration is as shown in (c). Note that, similar to the two-layer flexible substrate described above, the configurations of the four-layer and single-layer flexible substrates shown in FIG. It is not limited.

In the flexible substrate 10 with the four-layer structure shown in FIG. 14A, in the third layer where the VH wiring 1402 of high potential liquid is formed, a guard pattern 602 is formed near one side 10c in order from the side 10c side. , a VSS wiring 606, and an anode signal line 604 are formed. A VH wiring 1402 is formed next to the anode signal line 604. In this case, due to the ink entering the third layer from the side portion 10c, the VSS wiring 606 and the anode signal line 604 are short-circuited before the ink reaches the VH wiring 1402, causing an abnormality in the print head. can be detected.

In the flexible substrate 10 with the four-layer structure shown in FIG. 14(a), both sides of the GNDH wiring 702 are surrounded by VSS wiring 606 in the fourth layer, but only the GNDH wiring 702 is formed in the fourth layer. You can also do this. In addition, in the flexible substrate 10 with the S4 layer structure shown in FIG. 14A, the structure consisting of the guard pattern 602, the VSS wiring 606, and the anode signal line 604 is arranged only in the third layer on the side portion 10c side with respect to the VH wiring 1402. are doing. However, for example, if the VH wiring 1402 is formed with a wide width close to the side portion 10d, a similar configuration will be formed on the side portion 10c side as well. Further, for example, if the VH wiring 1402 is formed near the side 10c or 10d of another layer, the guard pattern 602, the VSS wiring 606, and the anode signal are placed closer to the side than the VH wiring 1402. A structure defined by line 604 will be formed.

In the four-layer flexible substrate 10 shown in FIG. 14(b), the first, second, and third layers have the same configuration as the four-layer flexible substrate 10 shown in FIG. 9(a). ing. In the fourth layer, a guard pattern 602, a VSS wiring 606, and an anode signal line 604 are formed on the side part 10c side of the GNDH wiring 702 provided on the side part 10c side. As a result, even if ink enters from the side portion 10c in the fourth layer, the VSS wiring 606 and the anode signal line 604 are short-circuited before the ink reaches the high-potential GNDH wiring 702, and the print head is damaged. It is possible to detect that an abnormality has occurred.

In the single-layer flexible substrate 10 shown in FIG. 14(c), a high-potential GNDH wiring 702 and a VH wiring 1402 are formed on the side portion 10d side. Further, a guard pattern 602, a VSS wiring 606, and an anode signal line 604 are formed on the side portion 10d side in this order from the side portion 10d side. As a result, even if ink enters from the side portion 10d, it is detected that an abnormality has occurred in the print head due to a short circuit between the VSS wiring 606 and the anode signal line 604 before ink from a high potential wiring reaches the ink. can do.

(2) In the above embodiment, the guard pattern 602 is provided on the side of the wiring section 603, but the present invention is not limited to this. That is, without providing the guard pattern 602, only the wiring portion 603 may be provided on the side of the high potential wiring. This shortens the time it takes to detect that an abnormality has occurred in the print head after the ink begins to enter the flexible substrate 10, but it is possible to detect the abnormality as in the above embodiment. It is.

(3) In the above embodiment, the wiring portion 603 is provided on the wiring side with a higher potential than the guard pattern 602, but the present invention is not limited to this. That is, only the guard pattern 602 may be provided on the sidemost side without providing the wiring portion 603. Thereby, even if the ink starts to enter the flexible substrate 10, time can be gained until the high potential wiring is short-circuited with other wiring due to the ink.

(4) The embodiments described above and the various forms shown in (1) and (3) above may be combined as appropriate.

10, 900, 1000 Flexible board 602 Guard pattern 603 Wiring section 604 Anode signal line 606 VSS wiring

Claims (12)

It is connected at the end side to a recording element substrate capable of ejecting ink using a recording element, and is capable of transmitting a signal from a control unit in a recording device to the recording element substrate via wiring, and A flexible printed circuit board capable of transmitting a signal from the recording element substrate toward the control section,
On the side of the high-potential wiring, there is a regulating part that restricts ink from entering into the flexible printed circuit board , and a signal value transmitted by the low-potential ground wiring and the control part, or an operation based on the signal is monitored. and a wiring section consisting of a low potential signal line ,
The flexible printed circuit board , wherein the regulating portion, the low potential ground wiring, and the signal line are arranged in order from the side portion side . The flexible printed circuit board according to claim 1 , wherein the regulating portion is formed of a metal material. The flexible printed circuit board according to claim 2 , wherein the regulating portion is not electrically connected. The flexible printed circuit board according to claim 2 , wherein the regulating portion is connected to an independent ground wiring. The flexible printed circuit board according to claim 1 , wherein the regulating portion is formed of a non-conductive material. 6. The flexible printed circuit board according to claim 1, wherein the signal line is a wiring for transmitting a latch signal for determining data. 6. The flexible printed circuit board according to claim 1, wherein the signal line is a wiring that transmits a signal from a temperature sensor provided on the recording element substrate. The flexible printed circuit board according to any one of claims 1 to 7 , wherein the regulating portion and the wiring portion are formed uniformly on the side portion side. The flexible printed circuit board according to any one of claims 1 to 7 , wherein the regulating part and the wiring part are formed only in a region corresponding to the high potential wiring on the side part side. . 10. The flexible printed circuit board according to claim 1, wherein the low potential is 6V or less, and the high potential is 10V or more. The flexible printed circuit board according to any one of claims 1 to 10 , wherein the regulating portion and the wiring portion are formed in a plurality of layers. a recording element substrate capable of ejecting ink by driving the recording element;
A recording head comprising: the flexible printed circuit board according to any one of claims 1 to 11 .

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